whats the differance between the 2
Slinky is a generic term that EB labels all their strings with, generally meaning easy to play I guess. As far as I can tell, they only use the word Skinny for 'Skinny top, heavy bottom' strings, which is a hybrid set designed to make it easy to solo on a downtuned guitar
Neither is a 'proper' guitar term, just something Ernie Ball uses for marketing. It's the string gauge that matters.